Scaffold native Android build and enforce Rust boundaries (#89)

android/features/src/main/res/values/strings.xml

@@ -0,0 +1,5 @@
+<resources>
+    <string name="app_name">IronStorage</string>
+    <string name="scaffold_title">No Password Store</string>
+    <string name="scaffold_detail">Your password store has not been configured.</string>
+</resources>